(1) Field of the Invention
The present invention relates to a transducer which directly converts mechanical vibrations into a digital signal. More specifically, the present invention relates to a digital microphone wherein acoustic energy may be directly converted into a digital signal.
(2) Description of the Prior Art
There are numerous advantages of storing information in a digital format. For example, digital data storage often enhances and accelerates duplication, reproduction and distribution processes. Additionally, unlike other forms of data storage, digital storage enables comprehensive and sophisticated analysis and modification of stored data with little or no degradation of the data. These benefits have been used to restore, preserve, enhance, analyze and duplicate audio signals and recordings. However, many of the benefits of digital storage and processing are not fully realized when applied to acoustic signals due to inherent limitations in the process of converting acoustic signals to digital data.
The process of converting acoustic signals to digital data typically involves two conversions. First, the acoustic signal is converted to an analog signal using a conventional microphone or similar device. Second, an analog to digital converter (A/D converter) is employed to convert the analog signal to digital data. Both conversions are susceptible to noise and distortion. While high-speed, high-accuracy microphones and A/D converters can reduce the susceptibility to and the amount of noise and distortion, they do not eliminate it. Additionally, such high-speed, high-accuracy equipment is expensive, making its use prohibitive for many applications.
Eliminating a conversion step removes noise and distortion associated with that step as well as eliminating the possibility of compounding any noise or distortion introduced in previous conversion steps. Digital microphones, such as those described in U.S. Pat. No. 3,286,032 and U.S. Pat. No. 4,422,182, produce digital data directly from an acoustic signal, thus reducing the number of conversions required from two to one. However, such digital microphones generally suffer from one or more disadvantages which limit their use for many applications.
One such disadvantage is the limited sensitivity to and resolution of acoustic signals typically available from digital microphones. Digital microphones generally are not capable of providing the resolution required for high fidelity audio recordings such as that required for digital audio tape and compact audio disk recordings. Furthermore, prior art microphones such as the one described in U.S. Pat. No. 4,422,182, typically require large complex patterns detailing every possible bit pattern superimposed on a reflecting surface or an optical array. The use of such conventional digital microphones is also limited because they generally require complicated circuitry which increases the cost and size of the microphones. The size, cost, and complexity of digital microphones, as well as the low resolution often associated with them, make the use of conventional digital microphones prohibitive for many applications.